In several data transmission systems, the linearity of a power amplifier limits the obtainable maximum transmission power, especially when the Peak-to-Average Ratio of a transmissible signal is high. In such a case, high power or amplitude values may temporarily occur in a signal to be fed into the power amplifier that have to be taken into account when the power amplifier is being dimensioned. In practice, this means that the input signal of the amplifier must be scaled to a lower power or amplitude level in order to fulfil the spectrum requirements of the data transmission system in use. What this method, referred to as back off, provides is that a signal to be amplified is located within an area, where the transmission function of the amplifier is more linear. However, a problem arises, since back off reduces the efficiency of the amplifier and/or the transmitter. Then again, the power amplifiers having a broad linear operating range are expensive and the efficiency thereof is very poor.
Different limiting, or clipping, methods concerning the power or amplitude values of signals have been developed in the background art. However, the prior art methods generally alter the signal in such a manner that in code division multiple access systems the orthogonality of different user-specific codes is no longer maintained. Occasionally the power or amplitude of transmission cannot be limited in practice in order for the detection in the receiver of the subscriber device to be successful, since a multilevel modulation method is used, in which the symbols are placed so close to one another in a signal space diagram that even the slightest increase in noise causes an error in the detection. The clipping should therefore be focused on those transmissions only that can be clipped. Examples of systems that cannot endure signal clipping are the 3GPP (3rd Generation Partnership Project) and the HSDPA (High Speed Downlink Packet Access) studied by the standardization forum.